Focal-plane shutter



March 18, 1947.

L. w. G ACKI FOCAL PLANE SHUTTER- Filed Feb. 2, 1945 2 Sheets-Sheet lINVENTOR Leonm'd Wyac/ri My? f mms March 18, 4 w GACK] FOCAL PLANESHUTTER FiledFeb. 2, 1945 2 Sheets-Sheet 2 I INVENTOR Lennard W 9610126a The end 24a of shaft 24 is secured in a spring loading knob 26, thisknob having a reduced hub 2.? (Figure 4) on which is formed a lobe 23.Lobe 28 is provided with a cam surface 280. and an abutment surface orstop 2% which coact respec tively with the arms 29 and 3%) of anescapement generally indicated at 3!. Escapement 3i is rockably mountedon the shank 32 (Figure 1) of a screw 33 threaded into side plate 65.Coiled about screw shank 32 is a spring 34, one end 34a of which isconnected to escapement 3i (Figure 4) and the other end 3% of which(Figure l) is connected to side plate 16 so that escapement 3i (Figure4) is maintained in the position shown;

wherein arm 30 is in the path of stop 2% of lobe 28. It may now be seenthat when knob 26 isrotated to load spring 25, lobe 28 (Figure 4) alsorotates. engages escapement arm 29, forcing the escapement clockwise topermit passage of the lobe. If the operator thereafter looses his graspon the loadin knob 26 (Figure 1) permitting spring 25 to unwind, thespring cannot completely unwind, as stop 28?) (Figure 4) will engage thetop of escapement arm 29 which is returned to its stopping position byspring 34. As loading of the spring 25 proceeds, cam surface 28a of theload engages escapement arm 3t, forcing the arm counterclockwise untilthe lobe passes into the position shown wherein the tendency of the lobeto rotate clockwise under the bias of the spring 25 has becomerestricted by the engagement of lobe stop 2% with the abutment 39aformed on escapement arm 39. Thusthe tension of the shutter operatingspring 25 may be set in small increments so that a wide range of springtensions, and hence shutter speeds, may be selectively attained.

Curtain l3 comprises a leading curtain 34 and a trailing curtain 35.Curtain 34 has its righthand end attached to winding roll ii in anysuitable manner, and on the left-hand edge is secured a rigid bar 36,the length of which exceeds the width of the curtain; thus the length ofbar 36 equals substantially the distance of frame side plates 16 and I1while curtain 34 is only slightly wider than aperture 2!.

I The left-hand end of trailing curtain teis secured to rewind roll 12,while to the right-hand edge of this curtain is secured a rail 37somewhat similar to rail 35 in that its length exceeds the Width ofcurtain 35, the curtain being slightly wider than-aperture 2!. Rails 36and 371 when separated accordingly define slit M of curtain l3 and thewidth of this slit may be varied between limits as will be describedhereinbelow.

Rewind roll I2 comprises a hollow tube, the oppositeends of which aresecured to collars 38 and 39 respectively, and these collars arerotatably mounted on a shaft M3. The opposite ends- Mia and 58b of shaft40 are reduced and have fastened respectively thereto hollow ribbondrums ii and 42. Drum il includes a hub 33 which with the periphery ofthe drum forms an annular space 44 within which a torsion spring 45 iscoiled about the hub. One end 65a of this spring is secured to drum 4i,and the other end 45b thereof is fastenedto rewind roll collar 33, thisspring being provided for a purpose which will be described hereinbelow.The left-hand end of a ribbon 46 is attached to drum 4i, and this ribbonis disposed within frame it! between side plate 5 and trailing curtain35. Ribbon 46 is trained about a small roller d8 rotatably mounted inthe upper end of curtain bar 36 and its end As the lobe rotates, its camsurface 280a 6a is securely fastened to the upper end of trailingcurtain bar 31.

Lower ribbon drum 42 has secured thereto the left-hand end (as viewed inFigure 1) of a ribbon 4?, this ribbon being trained over a small rolleriSa rotatably mounted on the lower end of leading curtain bar 36; theend lla of this ribbon is securely fastened to the lower end of thetrailing curtain bar 31. It will thus appear that the slit definingedges of the leading and trailing curtains are adjustably securedtogether and the width of slit It may be determined, as will bedescribed, bythe extent to which ribbons "t6 and ii are unwound fromtheir respective drums 4'!" and '42.

As will more clearly appear hereinbelow, shutter curtain i3 andaccordingly slit M (Figure 1) shutter l3 travels from right to left (asviewed in Figure 1). These features are particularly desirable when rollfilm is being used, as they make possible much more rapid operation ofthe camera, uniform exposure of the film, and preclude fogging of thefilm.

To attain these ends, ribbon drum 4 2 is provided with an arcuate slot49' (Figure 6), and collar 39 of rewind roll l2 (Figure 1) has a numberof holes 59 drilled therein (see'also Figures 3 and 6). The centers ofthese holes lie along the circumference of a circle the radius of whichis equal to that of a circle whose circumference coincides with thecenter line of slot 49 so that the holes and slot 49 are in registry forpurpose to be described. Collar 39 also has secured thereto andextending therefrom into slot 49 a pin 5! (Figure 6) which accordinglylimits the amount of relative movement possible between the collar anddrum 42 to the arcuate length of slot 49. Thus relative movement betweenrewind roll l2 and ribbon drums il and 42 under the bias of spring 45(Figure 1) is equally limited. It is by reason of the provision of thislimited relative movement between the rewind roll and the ribbon drumsthat slit 14 may be selectively adjusted, the desired width beingpredetermined by mechanism to be described.

Mounted on end 48b of shaft 60 (Figure 1) is a sleeve generallyindicated at 52. This sleeve includes a flange 53 disposed within drum42, a reduced hub 54 which has a sliding fit on shaft end 4%, and ashell 55 hollowed out to a diameter in excess of that of shaft end 4% toprovide an annular space 56 within which a spring 57 is coiled about theshaft. The upper end of this spring (as viewed in Figure l) bearsagainst an interior shoulder 55a formed by the shell 55 and hub 5 3 ofsleeve 52, and the lower end bears against the head of a screw 58threaded into the lower end of shaft end 40b. A knurled knob 5.9 issecured to the free end of shell 55 as by a set screw 5!) for thepurpose of manipulating the sleeve. It will now appear that sleeve 52may be slid axially of shaft end 49b against the bias of spring 57 whichtends to hold the sleeve in the position shown, and the sleeve may alsobe rotated about the shaft end 40b.

Sleeve flange 53 has secured thereto a pin 6! (see also Figure 6) whichextends through slot 49 in drum 42 and selectively into any one of holes50 in roll drum 39. The width of slit I4 is determined by that one ofholes 50 into which pin 61 is set. Thus sleeve 52 may be drawn away fromroll collar 39 until pin 61 clears the collar. Thereafter the sleeve maybe rotated in one direction or another and pin 6! set into that one ofholes 50 selected in accordance with the slit width desired. The mannerin which the setting of pin 61 predetermines the width of slit 14 willbe described hereinbelow.

The upper end 40a of shaft 40 (Figure 1) extends through and isjournaled in frame side plate l6 and has secured thereto a small pinion62. This pinion meshes with a gear 63 rotatably mounted on a stud 64,the lower end of which is fastened to side plate I 6. On opposite sidesof gear 63 are respectively secured, as by screws 65, a. ratchet 6B anda rewind knob 61, these three parts being held in operative position onstud (it by the head of a screw 68 the shank of which is threaded intothe free end of the stud. A spacer 69 is provided between ratchet 66 andside plate 16 to hold gear 63 in mesh with pinion 62.

As is more clearly shown in Figure 5, ratchet 66 coacts with a pawl 10pivotably mounted on the unthreaded portion of a screw 'H (see Figure 1)threaded into side plate I6. One end of pawl Ill is, of course, providedwith a detent 12 which coacts with ratchet 66, and the other end of thepawl (Figure 2) carries a knob 73 by which the pawl may be manipulated.A sprin 14 has one end attached to the pawl and the other end to a pin15 fastened to side plate 16, and this spring constantly biases the pawlinto ratcheting engagement with the ratchet. Thus it will appear thatwhen pawl 10 is pivoted clockwise (as viewed in Figure 5) to free detent12 from ratchet 65, shaft 40 (Figure 1) and accordingly shutter l3 arereleased for exposure operation by the spring driven winding roll H.

In order to limit the exposure and rewind travel of shutter [3 acrossaperture 2|, ratchet 66 (Figure 5) has secured thereto a pin 75 whichtravels with the ratchet during its clockwise and counterclockwisemovement. Counterclockwise movement of the ratchet is limited by theabutment of pin 76 with a fixed pin 11 secured to side plate [6 (Figurel) and clockwise movement of the ratchet is limited by the abutment ofits pin '16 (Figure 5) with another fixed pin 18 secured to side plateIt. Clockwise movement of ratchet 65 occurs while the curtain [3 (Figure3) is being rew'ound, and of course the ratchet rotates counterclockwiseduring exposure operation of the curtain when the curtain is being woundon winding roll II.

In the following description of the operation of the above structure,when reference is made to the setting position of shutter l3 (Figure 1),the midway position of the shutter, and the final position of theshutter, it will be understood that when in the setting position,curtain bars 35 and 31 are capped, i. e. they overlie one another at theleft-hand portion of frame I!) adjacent rewind roll I2, that when in themidway position the curtain bar are spaced to define slit 14 as shown inFigure 1, and that when in the final position, the curtain bars arecapped and lie in the right-hand portion of frame [0 adjacent windingroll H. In this connection, the setting 6 position of the curtain barsis determined by the engagement of pin 16 (Figure 5) and pin [8.Engagement of pin 16 with pin 17, on the other hand, determines thefinal position.

Prior to the exposure operation of the shutter, curtain bars 35 and 3loverlie or cap one another in the setting position. To select the slitwidth desired, knob 59 is pulled outwardly of frame It to withdraw pin5! from roll collar 39. Thereafter the knob is rotated until pin 5! canbe reinserted in collar 39 into the selected hole. When the curtain isin the setting position, operating spring 25 is under tension so thatrelease operation of pawl H! by knob 13 releases the pawl detent fromratchet 68. Thence, spring 25, acting through roll H, shutter i3 andribbon drums 4i and 42, rotates shaft 4i! and accordingly gears 62 and63. During the initial part of this operation, curtain as andaccordingly bar 33 start their movement from the setting position to theright. However, curtain 35 and bar 3? do not partake of this initialmovement being held in the setting position due to the bias of spring 25which at all times biases rewind roll 12 in such a direction as to tendto pull curtains 35 to the left. Accordingly, during the initialmovement of curtain 34 and bar 36, ribbons itand d! are unwound fromtheir respective drums 4i and 42. Drum 32 continues to rotate relativeto rewind roll collar 33 until pin 8! is engaged by the end of slot 49.Upon this engagement drum 42 and collar 39 are in effect locked togetherso that continued rotation of the drum rotates roll l2, permittingcurtain 35 to unwind therefrom at the same rate at which the ribbons arebeing unwound from their drums. Thus it follows that slit it is formedand is maintained at a constant width during the travel of curtain i3from its setting to its final position as bar 35 is the only thing thatis drawing bar 32' and accordingiy curtain 55 over aperture 2 i. Inother words, curtain has no independent relationship to ourtain 34 butdepends on the movement of curtain 34 for its movement. Before, curtainI3, or rather before bar 8, attains the final position, pin it (Figure5) engages stop pin ll which, acting through the train of gears 63 andG2 and shaft 49, stops rotation of drums 4i and E2. However, bar 35continues to move to its final position, and in so doing, pulls againstthe bights in ribbons 46 and ii to shorten the overlying ends thereofattached to bar 3? and hence draw bar 3'! toward bar 36 until the twobars are capped.

When it is desired to rewind curtain 13 from the final position to thesetting position, knob 67 is rotated clockwise (as shown in Figure 5)until pin 16 engages pin l8. During this rewind operation, curtain bars36 and 37 remain capped as the ribbons 46 and ii, while being rewound ontheir drums ti and 12 respectively, constantly force the bars togetherwhile at the same time drawing them to the left.

It may accordingly be seen that the width of slit i4 may be selected orvaried at any position of curtain IS with no tension on the setting knob59. It also follows that inasmuch as curtain 35 is driven solely bycurtain 34, it must of necessity follow curtain 34 at a uniform rate andhence both the leading and following curtains accelerate and decelerateat the same rate to form a slit of uniform width. Still further, whenthe curtain attains its final position, the slit dividing bars 36 and 31automatically becomes capped, or rather recapped, and remains so duringthe rewind operation, thus greatly facilitating the use of the shutterwith roll film.

Accordingly, I have provided a shutter which attains the several objectsset forth hereinabove in a thoroughly practical and efficient manner.

As many possible embodiments may be made of the above invention, and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth, or shown in theaccompanying drawing, is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. A focal plane shutter, in combination, a casing, a pair of spacedshafts rotatably mounted in said casing, a tension roller mounted on oneof said shafts, arewind roller rotatably mounted on the other of saidshafts, means limiting the relative movement between said rewind rollerand its shaft, a pair of ribbon drums secured to said rewind rollershaft, a leading curtain connected to said tension roller, a followingcurtain connected to said rewind roller between said ribbon drums, apair of ribbons, each of said ribbons having one end connected to one ofsaid drums and its other end connected to said following curtain, meansconnecting each of said ribbons to said leading curtain for bothmovement therewith and movement relative thereto, means for spacing theadjacent edges of said curtain to form an exposure slit adapted to beswept across an aperture between said rollers upon exposure operation ofsaid shutter, means biasingsaid rewind roller oppositely to thedirection of rotation of said ribbon drums during exposure opera tionthereof, and means effective after the free edge of said leading curtainhas passed beyond said aperture for holding said "tape drums againstfurther movement, whereby continued movement of said leading curtainfree edge cause relative movement between said leading curtain and saidribbons, causing the adjacent edges of said curtain to be drawn togetherin capped relationship.

2. A focal plane shutter, in combination, a casing, a pair of spacedshafts rotatably mounted in said casing, a tension roller mounted on oneof said shafts, a rewind roller rotatably mounted on the other of saidshafts, means limiting the relative movement between said rewind rollerand its shaft, a pair of ribbon drums secured to said rewind rollershaft, a leading curtain connected to said tension roller, 9. followingcurtain connected to said rewind roller between said ribbon drums, apair of ribbons, each of said ribbons having one end connected to one ofsaid drums and its other end connected to said following curtain, meansconnecting each of said ribbons to said leading curtain for bothmovement therewith and movement relative thereto, means for spacing theadjacent edges of said curtain to form an exposure slit adapted to beswept across an aperture between said rollers upon exposure operation ofsaid shutter, means biasing said re windroller oppositely to thedirection of rota tion of said ribbon drums during exposure operationthereof, and means for effecting relative movement between said adjacentedges after said edges have passed over said aperture to cause saidedges to overlie one another thereby to recap said shutter.

3. A focal plane shutter, in combination, a casing, a pair of spacedshafts rotatably mounted in said casing, a tension roller mounted on oneof said shafts, a rewind roller rotatably mounted on the other of saidshafts, means limiting the relative movement between said rewind rollerand its shaft, a pair of ribbon drums secured to said rewind rollershaft, a leading curtain connected to said tension roller, a followingcurtain connected to said rewind roller between said ribbon drums, apair of ribbons, each of said ribbons "ation thereof, means foreffecting relative movement between said adjacent edges after said edgeshave passed over said aperture to cause said edges to overlie oneanother thereby to recap said shutter, and means for maintaining saidadjacent edges recapped as the shutter is re wound.

4. Apparatus according to claim 1 wherein the means which biases therewind roller oppositely to the direction of rotation of the ribbondrums comprises a spring having one end attached to one of the ribbondrums and the other end attached to the rewind roller.

5. Apparatus according to claim 1 wherein the means which biases therewind roller oppositely to the direction of rotation of the ribbondrums comprises a coiled spring disposed within one of said ribbon drumsand having one end secured to said ribbon drum and its other end securedto said rewind roller.

LEONARD W. GACKI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

